Cycles / OSL: Updare stdosl.h to 1.7.1.

This updates our file to OSL 1.7.1, which comes with some new inbuilt
features:

- linearstep()
- smooth_linearstep()

- hash()
- getchar()

intern/cycles/kernel/shaders/stdosl.h

@@ -433,6 +433,35 @@ normal step (normal edge, normal x) BUILTIN;
 float step (float edge, float x) BUILTIN;
 float smoothstep (float edge0, float edge1, float x) BUILTIN;
 
+float linearstep (float edge0, float edge1, float x) {
+    float result;
+    if (edge0 != edge1) {
+        float xclamped = clamp (x, edge0, edge1);
+        result = (xclamped - edge0) / (edge1 - edge0);
+    } else {  // special case: edges coincide
+        result = step (edge0, x);
+    }
+    return result;
+}
+
+float smooth_linearstep (float edge0, float edge1, float x_, float eps_) {
+    float result;
+    if (edge0 != edge1) {
+        float rampup (float x, float r) { return 0.5/r * x*x; }
+        float width_inv = 1.0 / (edge1 - edge0);
+        float eps = eps_ * width_inv;
+        float x = (x_ - edge0) * width_inv;
+        if      (x <= -eps)                result = 0;
+        else if (x >= eps && x <= 1.0-eps) result = x;
+        else if (x >= 1.0+eps)             result = 1;
+        else if (x < eps)                  result = rampup (x+eps, 2.0*eps);
+        else /* if (x < 1.0+eps) */        result = 1.0 - rampup (1.0+eps - x, 2.0*eps);
+    } else {
+        result = step (edge0, x_);
+    }
+    return result;
+}
+
 float aastep (float edge, float s, float dedge, float ds) {
     // Box filtered AA step
     float width = fabs(dedge) + fabs(ds);
@@ -455,8 +484,9 @@ float aastep (float edge, float s) {
 
 
 // String functions
-
 int strlen (string s) BUILTIN;
+int hash (string s) BUILTIN;
+int getchar (string s, int index) BUILTIN;
 int startswith (string s, string prefix) BUILTIN;
 int endswith (string s, string suffix) BUILTIN;
 string substr (string s, int start, int len) BUILTIN;